Use the console.
Hit the ~ key (BEFORE each line) and type:
(~) DebugMode 1 (Hit Return)
(~) dm_givelevel x (x=no. of levels) (Hit Return)
Your cursor should change to target mode, click on your character to give him the x no. of levels. To finish off, type:
(~) DebugMode 0 (Hit Return)
Note: the syntax in each line is very important. Make sure you type this exactly as shown above.
If you don't have the ~ symbol on your keyboard, click in the chatbox at the bottom of the screen and type:
##DebugMode 1 (Return)
##dm_givelevel x (Return) (Click on character to give levels)
##DebugMode 0 (Return)
Which should work all the time.
Don't try to play in DebugMode 1, weird things happen!
This is an older post of mine. The above advice will allow you to level up to 40 if you desire to test a certain build.
